1. Field of the Invention
One embodiment of the present invention relates to a semiconductor device including an oxide semiconductor and a manufacturing method thereof.
In this specification, the term semiconductor device refers to all devices that can function by utilizing semiconductor characteristics, and electrooptic devices, semiconductor circuits, and electronic devices are all semiconductor devices.
2. Description of the Related Art
In recent years, transistors are used for many liquid crystal display devices and light-emitting display devices typified by flat panel displays, and they are formed with silicon semiconductors, such as amorphous silicon or polycrystalline silicon, over a glass substrate.
Attention has been directed to a technique in which, instead of such silicon semiconductors, oxide semiconductors are used for transistors.
Examples of the oxide semiconductor include zinc oxide, which is one-metal oxide, and In—Ga—Zn—O-based oxide, which is a homologous compound. Techniques have been disclosed in which such an oxide semiconductor is used to form transistors as switching elements and the like in pixels of a display device (see Patent Documents 1 to 3).